The present application relates to metal-to-metal antifuses fabricated using carbon-containing antifuse layers, and more particularly, to programming metal-to-metal antifuses that are fabricated using carbon-containing antifuse layers.
Metal-to-metal antifuses are well known in the art. These devices are formed above a semiconductor substrate, usually between two metal interconnect layers in an integrated circuit and comprises an antifuse material layer sandwiched between a pair of lower and upper conductive electrodes, each electrode in electrical contact with one of the two metal interconnect layers.
Numerous materials have been proposed for use as antifuse material layers in above-substrate antifuses. Such materials include amorphous silicon or an alloy thereof, poly silicon, crystalline carbon, silicon, germanium, chalcogenide elements.
The integration of copper and low −K dielectric are regarded among other materials as a promising use for reducing the resistance/capacitance delay (RC delay). To prevent copper diffusion and to help adhesion, a thin barrier layer is desirable between the antifuse material layer and the metal layer. A titanium nitride (TiN) barrier layer, presently in use with an amorphous silicon antifuse layer at a low programming current, for example below 1 milliAmp (mA), has a very high resistance and is nonlinear. For example, the resistance for an amorphous silicon antifuse layer having a TiN barrier layer for a programming current below 1 mA can be many thousands or ten thousands of ohms and may be non-linear (i.e., acting like a diode). The TiN barrier layer, used with a carbon base antifuse at low programming current (i.e., below 5 mA) when compared to a TiN barrier layer used with an amorphous silicon layer, has considerably lower resistance of about 2000 ohms at about 1.0 mA and about 300 to about 500 ohms at about 5 mA, and, in both cases, is linear.
Hence, there is a need for a barrier metal layer for an antifuse that has a low resistance at a low programming current and a good switching character ratio.